The design of bows for use in archery has evolved over thousands of years. Changes in technology have been the result of mechanical innovation and advancement in material science. One significant advancement in bow design was the development of the “compound” bow. Traditional bows are referred to as “recurve” bows. Recurve bows are usually made from wood and must be bent into the curved bow shape each time a user wishes to attach the bow string. Recurve bows employ a single bow string and the resilience of the bow places the bow string in tension. While effective, it usually requires a great deal of force to draw the bowstring back when using a recurve bow. Contrastingly, compound bows employ a camming system that allows a user to exert less force on the bow string to draw it back than is necessary with a similarly rated recurve bow.
Major components of compound bows are the riser (on which a handle is mounted or formed) and two generally opposed limbs, each extending from an end of the riser. The limbs may be mounted in pockets at the ends of the riser and have pulleys or cams rotatably attached to the distal ends of each limb. A drawstring and harness system is wound between the pulleys and cams. Upon drawing the drawstring back, the limbs flex to allow the drawstring and the harness system to be loaded under high tension. In turn, the riser is loaded as a result of bending and torsional forces transferred thereto. These forces are resolved in the riser as tension, compression, shear forces, and torque.
Typically, the riser is fabricated from metal such as aluminum or magnesium or from composite materials that generally lack any appreciable amount of elasticity. The limbs, on the other hand, are typically fabricated from a material having a sufficient amount of resiliency (for example, woven unidirectional epoxy fiberglass and/or co-mingled composite materials) to allow them to flex or bend, thereby placing the bowstring in tension. Accordingly, upon drawing the bowstring back on a bow having a riser fabricated from a substantially inelastic material and limbs that are by comparison more flexible, undesirable stresses are introduced into the bow, particularly at the joints between the riser and the limbs. Over time, these stresses may compromise the structural integrity of the bow.
Furthermore, in bows and crossbows having risers fabricated from substantially inelastic materials, the opportunity for stress-related cracking to develop as a result of repeated use increases. Climatic changes (e.g., high temperature that results in increased creep or degradation of the composite matrix or the adhesives used, variations in humidity, and the like) can also contribute to the deterioration of the microstructure of the material of the riser, which can in turn significantly reduce the useful life of the bow. Moreover, deterioration of the microstructure can lead to visible defects in the riser that detract from the overall appearance of the bow.
Based on the foregoing, it is the general object of the present invention to provide an archery bow having components fabricated from a material that overcomes the problems of, or improves upon, the prior art.